1. Field of the Invention
The embodiments of the invention generally relate to an end effector assembly for handling large area substrates in a processing system.
2. Background
Flat panel displays—such as active matrix, or thin film transistor (TFT) displays, liquid crystal displays (LCD), plasma displays, and the like—are commonly used in such applications as computer and television monitors, cell phone displays, personal digital assistants (PDAs), and an increasing number of other devices. Generally, flat panel displays comprise two glass plates having a layer of liquid crystal materials sandwiched therebetween. At least one of the glass plates includes one conductive film disposed thereon that is coupled to a power source. Power, supplied to the conductive film from the power source, changes the orientation of the crystal material, creating a pattem display.
With the marketplace's acceptance of flat panel technology, the demand for larger displays, increased production, and lower manufacturing costs have driven equipment manufacturers to develop new systems that accommodate larger size glass substrates for flat panel display fabricators. Current glass processing equipment is generally configured to accommodate substrates up to about one square meter. Processing equipment configured to accommodate even larger substrate sizes is envisioned in the immediate future.
Glass substrate processing is typically performed by subjecting a substrate to a plurality of sequential processes to create devices, conductors, and insulators on the substrate. Each of these processes is generally performed in a process chamber configured to perform one or more steps of the production process. In order to efficiently complete the entire sequence of processing steps, a number of process chambers are typically coupled to a central transfer chamber that houses a robot to facilitate transfer of the substrate between the process chambers. Processing platforms having this configuration are generally known as cluster tools. Such cluster tools for glass substrate processing are available from AKT, Inc., a wholly-owned subsidiary of Applied Materials, Inc., of Santa Clara, Calif.
As glass substrates increase in size, the manufacturing equipment for handling and processing these substrates must become larger as well. The increased size of substrate handling equipment, such as the transfer robot mentioned above, has created a number of technical challenges that must be overcome in order to maintain accurate substrate transfer. For example, one transfer robot used to handle flat panel substrates has a series of cantilevered end effectors supported from a wrist that support that underside of the substrate. However, the long end effectors required to adequately support large area substrates are subject to “droop”, or sag. The sag of the end effector must be accommodated by greater range of robotic motion and/or greater component clearance, both of which undesirably lead to higher tool costs.
The end effector may be made of a single piece of ceramic to minimize droop due to the high Young's modulus of ceramic materials. However, as ceramic shrinks by 20–30 percent upon baking, furnaces need to be at least 20–30 percent larger than the final product. Furnaces of such capacity are not readily available for end effector production. Therefore, it is difficult to make large one-piece end effectors to accommodate larger substrates due to furnace size limitations and high costs associated with their manufacture.
Therefore, there is a need for an end effector to accommodate large substrates.